1. Field of the Invention
The present invention relates to an image forming apparatus in which visibility of a sheet path in a main body frame is improved for jam countermeasures or the like, and an operation method of the image forming apparatus.
2. Description of the Related Art
In an image forming apparatus such as a laser printer or a digital copier, as disclosed in JP-A-2007-219420, a so-called automatic duplex unit (ADU) is provided to reverse a sheet one side of which is printed and to again convey it to an image forming section, so that both sides of the sheet can be printed.
In general, in this kind of image forming apparatus, a specified image is transferred in an image forming section to a sheet fed one by one from a sheet feeding section, and the image transferred to the sheet is fixed by a fixing section. The sheet on which the image is fixed is ejected to a specified sheet ejection section, or is not ejected but is switched back and is sent to an automatic duplex unit. The sheet is again sent from the automatic duplex unit to the image forming section, and a specified image is printed also on the opposite side.
In the image forming apparatus as stated above, a relay unit is required which includes a conveyance switching mechanism for guiding the sheet after fixing from the fixing section to the specified sheet ejection section or for switching back it. Besides, an intermediate unit is also required which guides the sheet switched back from the relay unit to the automatic duplex unit. As stated above, there are plural sheet paths after the fixing, and these are suitably switched and used, and accordingly, a so-called jam can occur in which the sheet is jammed along the path in the middle of conveyance.
Here, since each of the relay unit and the automatic duplex unit can be constructed in one unit, it is easy that they can be constructed to be capable of being pulled out to the outside from the main body frame or can be constructed to be capable of being detached from the main body frame. Thus, even if a jam occurs in these sheet paths, a jam processing can be easily performed in the outside of the main body frame, not the narrow portion in the main body frame, without receiving spatial restriction.
On the other hand, a fixing section includes a high temperature fixing roller and is hard to handle, and is, together with power source lines for a heat source and switches for those, mounted in the main body frame. Besides, as described above, the intermediate unit is for guiding the sheet switched back by the relay unit to the automatic duplex unit, and is disposed near the fixing section because of the arrangement of the respective parts. Thus, it is difficult that the intermediate unit is construct to be capable of being pulled out to the outside of the main body frame, and is, together with the fixing section, fixed and placed in the main body frame also in view of the improvement of safety.
In the image forming apparatus having the structure as stated above, when a jam occurs, for the purpose of facilitating jam handling and maintenance, the relay unit is pulled out to the outside of the main body frame, and the automatic duplex unit is detached from the main body frame. A checker uses the space generated in the main body frame by the pulling out and the detaching of these to check a sheet path of the intermediate unit remaining in the main body frame, and performs the jam processing as the need arises.
However, since a guide member to guide the sheet switched back to the automatic duplex unit is provided along the sheet path in the intermediate unit, the visibility of the sheet path is bad, and there is a problem that even if a sheet remains in the intermediate unit by the occurrence of a jam, this is difficult to find, and the workability of the jam processing is bad.